This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. Section 119 from an application for xe2x80x9cALLOY-COATED OPTICAL FIBER AND FABRICATING METHOD THEREOF,xe2x80x9d filed earlier in the Korean Industrial Property Office on May 12, 2000 and there duly assigned Ser. No. 2000-25322.
1. Field of the Invention
The present invention relates generally to an optical fiber, and more particularly to an optical fiber with the cladding layer coated with alloy materials on its outer circumferential surface and a fabricating method thereof.
2. Description of the Related Art
Basically, optical fiber coating methods are classified into a polymer coating, a metal coating, and a mineral coating. In particular, the metal coating provides better sealing capabilities due to its feasibility during soldering and welding; thus, it is widely used for undersea cables. Moreover, the metal coating is stronger and better heat-proof when compared to other coating methods, and accordingly, it is more suitable to be used in many unfavorable circumstances. Some of the known materials used in the metal coating includes tin (Sn), aluminum (Al), zinc (Zn), indium (In), lead (Pb), gold (Au), and nickel (Ni).
FIG. 1 is a schematic view of a general optical fiber illustrating the metal coating principle. In FIG. 1, the regions I, II, and III represent an optical fiber, a frozen metal, and a melted metal, respectively. Reference characters V, r, z, H, and C, respectively, denote the optical fiber drawing speed, the distance from the center of the optical fiber, the distance along the optical fiber, the height from the bottom of a coater, and the melted metal for coating material.
As shown in FIG. 1, the thermal effect caused by the difference in the temperature between the optical fiber and the metal solution enables the metal solution to be coated on the outer circumferential surface of the optical fiber. The temperature of an optical fiber is at the room temperature, whereas the melted metal is at a relatively high temperature, for example, 200xc2x0 C. When the fiber is exposed to the metal solution with a vast difference in the temperature, the metal becomes instantaneously adhesive around the outer circumferential surface of the optical fiber.
Referring to FIG. 1, the mechanism of the metal coating is divided into a subcoating and an outercoating. The adhesive effect caused by the temperature differences is responsible for the subcoating, and the coating at the exit zone of the coater provides the outercoating. The relationship between the subcoating and the outercoating is expressed as:                                           h            o                    =                      0.64            ⁢                          xe2x80x83                        ⁢                                          b                ⁡                                  (                                                            3                      ⁢                      η                      ⁢                                              xe2x80x83                                            ⁢                      V                                        σ                                    )                                                            2                /                3                                                    ,                            (        1        )            
where h0 is the thickness of the outercoating, b is the thickness of the subcoating, xcex7 is viscosity, "sgr" is surface tension, and V is an optical fiber drawing speed.
The principle and method of coating an optical fiber with metal materials are disclosed in R. G. C. Arridge, A. A. Baker, and D. Cratchley, xe2x80x9cMetal Coated Fibers and Fiber Reinforced Metalsxe2x80x9d, J. Sci. Insts., vol. 41, p. 447, 1967. The paper discloses a dip method that is used in the metal coating process and explores some of the coating principle of an optical fiber, including the xe2x80x9cfreezing effectxe2x80x9d which describes the adhesive characteristics of the fiber and the coating materials.
In the paper, xe2x80x9cReductions in Static Fatigue of Silica Fibers by Hermetic Jackettingxe2x80x9d, Appl. Phys. Lett., vol. 34, p. 17, 1979.D.xe2x80x94written by A. Pinnow, G. D. Robertson, and J. A. Wysocki, explains the properties relating to the life of an optical fiber and how they are mainly limited by the static fatigue and that an aluminum-coated optical fiber lasts five times longer than a conventional polymer-coated optical fiber.
In another paper written by V. V. Bogatryrjov, E. M. Dianov, S. D. Rumyantesev, A. Y. Makerenko, S. L. Semenov, and A. A. Sysoljatin in xe2x80x9cSuper High Strength Hermetically Metal Coated Optical Fibersxe2x80x9d, SOV. Lightwave Commun., Vol. 3, P235, 1993, showed that an optical fiber fabricated by blocking the introduction of air as soon as the optical fiber is drawn from a preform and injecting nitrogen into the optical fiber exhibits a theoretical strength, approximately, about 14 Gpa.
In the conventional method of coating, a single metal, i.e., aluminum, has been typically used as coating material for an optical fiber. However, due to the limitations of physical characteristics in the single metal, it is not possible to control the properties of single metal materials to provide different performance as required in varying environment and communications applications.
It is, therefore, an object of the present invention to provide an alloy-coated optical fiber in which the coating performance is controllable according to its applications, and a method of fabricating the optical fiber.
It is another object of the present invention to provide an alloy-coated optical fiber with a higher bending strength without the phase separation, and a method of fabricating the optical fiber.
According to one aspect of the present invention, the core is formed of a light transmitting material, the cladding surrounds the outer circumferential surface of the core, and an indium-tin-silver coating layer is formed around the outer circumferential surface of the cladding.